steve@tellab3.UUCP (Steve Harpster) (06/05/85)
Has anyone figured out a way to do color graphics under Xenix 286 (on the IBM-PC/AT)? I'm currently working on a driver to do it but things are quite a bit tricky when running under protected mode on the 80286. Specifically, I want to change the video mode and write directly to display memory (address 0xb8000). As a related issue, Xenix sets the video mode to medium resolution. We have an EGA (Enhanced Graphics Adaptor) which doesn't like it. When you boot Xenix, the text is unreadable. It looks like the horizontal scan rate is wrong. You can flip a dipswitch on the EGA to emulate the CGA but that kind of defeats the purpose of buying the EGA in the first place. Does anyone know a boot hack to tell it to leave the adaptor alone? IBM claims ignorance with a "Sorry but we don't support it yet". Many thanks in advance. -- ...ihnp4!tellab1!steve Steve Harpster Tellabs, Inc.
robin@medstar.UUCP (Robin Cutshaw) (06/07/85)
To eliminate the reinitialization of the EGA in Xenix you must patch the
routine that does this...
cp /xenix /xenix-
adb -w /xenix -
$x
initCRTC+4?w cbc9 /* c756 = cbc9 */
$q
This will avoid initCRTC by just returning.
To use the color graphics adapter in graphics mode you will have to talk to
the controller. I have written (and extensively use) an I/O channel device
driver that will allow me to examine/modify any I/O address including the
graphics adapter and the PC Network Adapter. I may post this to net.sources
shortly. To actually write into graphics memory you will have to use some
of the defined macros in sys/param.h to get between kernel and physical memory.
This is what I use to DMA into/from the PC Network Adapter.
Good luck...
--
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Robin Cutshaw
uucp: ...!{akgua,gatech}!medstar!robin